Bonds from the city of denver with a face value of $1,000 each are selling at 110.611. if sean wishes to purchase three such bonds, how much can he expect to pay?

A bond quote (100.611) is the last price bond is traded at. A bond quote is the percentage of a face value. 
In this case, the bond quote is 110.611 which means that bond is traded at 110.611% of its face value.
If Sean wants to buy 3 bonds he needs to pay:
3*1000*110.611/100=$3318.33